This invention relates to a flushing liquid system for the wearing ring in a centrifugal pump which is particularly adaptable for use in the pumping of slurries in applications wherein excessive dilution of the latter cannot be tolerated, and to an improved wearing ring for use in said system.
Although liquid flushed wearing rings for use in centrifugal pumps are well known in the prior art as exemplified by U.S. Pat. No. 2,736,265 to Higgins, there are pumping applications in which the same do not prove particularly satisfactory in that excessive dilution of the liquid being pumped can result from the effect of the wearing ring flushing liquid.
For example in a pumping application for slurry, in order to prevent abrasion and rapid wear of the liquid flushed wearing ring in the centrifugal pump by the solids in the slurry, the percentage of solids in the slurry mixture will be optimized so as to in turn minimize friction losses and reduce excessive power expenditures.
This optimum percentage of solids to liquid in the slurry mixture can be very critical so that even small increases or decreases of solids to liquid in the slurry mixture will cause substantial increases in friction. Use of a prior art flushing liquid system for the wearing ring can under these conditions result in excessive and unacceptable dilution of the slurry.
Further, in those instances wherein the slurry mixture is prepared by the mixing of solid particles in a transporting liquid, the transporting liquid in essence becomes a necessary evil, and the pumping of any extra quantity of the transporting liquid beyond the minimum which renders the slurry mixture economically pumpable--as results from excessive dilution by the use of such prior art liquid flushed wearing ring--will result in an increase in the consumption of pumping energy for pumping the same.
In addition, many of the flushing liquid systems for wearing rings in the prior art do not include means for throttling the flushing liquid inlet flow and must accordingly operate at inordinately high flushing liquid inlet flow rates in order to insure that there will be sufficient flushing liquid to meet the requirements of the wearing ring throughout the entire operating range of the pump.
Further, in those locations where there is a scarcity of clear liquid for use in flushing the wearing ring, and/or dirty or contaminated liquids must be treated for use as flushing liquid, other functional and/or economic disadvantages are presented.
The present invention seeks to overcome these problems of the prior art by providing an improved flushing liquid system for the wearing ring of the centrifugal pumps and an improved wearing ring for use with the system which will act to optimize and minimize the flushing liquid required for the wearing ring and provide the additional advantage of minimizing dilution of the process fluid, slurry or other mixture being pumped by the associated centrifugal pump to which the improved wearing ring and flushing system is applied.